Mangroves buffer inland ecosystems from hurricane winds and storm surge. However, their ability to withstand harsh cyclone conditions depends on plant resilience traits and geomorphology. Using airborne lidar and satellite imagery collected before and after Hurricane Irma, we estimated that 62% of mangroves in southwest Florida suffered canopy damage, with largest impacts in tall forests (>10 m). Mangroves on well-drained sites (83%) resprouted new leaves within one year after the storm. By contrast, in poorly-drained inland sites, we detected one of the largest mangrove diebacks on record (10,760 ha), triggered by Irma. We found evidence that the combination of low elevation (median = 9.4 cm asl), storm surge water levels (>1.4 m above the ground surface), and hydrologic isolation drove coastal forest vulnerability and were independent of tree height or wind exposure. Our results indicated that storm surge and ponding caused dieback, not wind. Tidal restoration and hydrologic management in these vulnerable, low-lying coastal areas can reduce mangrove mortality and improve resilience to future cyclones.
This content will become publicly available on September 1, 2024
Physical model comparison of gray and green mitigation alternatives for flooding and wave force reduction in an idealized urban coastal environment
A 1:16 scaled physical model was constructed to investigate the effectiveness of a seawall, a submerged breakwater, and mangrove forests to mitigate overland flooding and forces on structures in an idealized urban coastal environment. The experiment was performed using tsunami-like waves at different water levels, wave amplitudes, and time scales to simulate long-wave dynamics. The baseline condition (no mitigation), seawall, submerged breakwater, and mangrove forest were tested individually, and the seawall and submerged breakwater were also tested in combination. Wave gauges, acoustic Doppler velocimeters, loadcells, and pressure gauges were used to measure wave elevations, velocities, forces, and pressures on coastal structures, respectively. The performance of these hard structures and mangroves was compared through their effects on wave elevation, particle velocity, and force reduction. Experimental results showed that each protecting structure reduced the horizontal wave forces and inland flow hydrodynamics in the low-water-level case, with a similar performance by the individual seawall, submerged breakwater, and four rows of mangroves. The combined configuration, when the seawall and submerged breakwater were installed simultaneously, caused the most significant maximum force percent reduction by approximately 50%, while mangrove forests arranged in eight rows resulted in a force reduction of 46% in the first building array. However, in the high-water-level cases, the impulsive force measured with the presence of the submerged breakwater was larger than in the baseline case; thus, the submerged breakwater may amplify the impulsive force on the vertical building rows for certain incident wave conditions. Generally, the combined hard structures induced the lowest force reduction factor measured in almost every building row compared to the seawall, submerged breakwater, and mangroves considered separately for all wave conditions and water levels. That means this multi-tiered configuration showed better performance than individual alternatives in reducing horizontal forces inland than the individual alternatives considered separately.
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- Award ID(s):
- 2110262
- NSF-PAR ID:
- 10487520
- Publisher / Repository:
- Coastal Engineering
- Date Published:
- Journal Name:
- Coastal Engineering
- Volume:
- 184
- Issue:
- C
- ISSN:
- 0378-3839
- Page Range / eLocation ID:
- 104339
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Coastal and nearshore communities face increasing coastal flood hazards associated with climate change, leading to overland flow and inundation processes in the natural and built environments. As communities seek to build resilience to address these hazards, natural infrastructure (e.g., emergent vegetation) and hybrid designs have been identified for their potential to attenuate storm-driven waves and associated effects in developed nearshore regions. However, challenges remain in robustly characterizing the performance of natural systems under a range of incident hydrodynamic conditions and in bridging interdisciplinary knowledge gaps needed for successful implementation. This paper synthesizes field and laboratory results investigating the capacity of Rhizophora mangle (red mangrove) systems to mitigate wave effects. Results indicate that R. mangle forests of moderate cross-shore width have significant effects on wave transformation and load reduction in sheltered inland areas. Opportunities for future interdisciplinary collaborations are also identified.more » « less
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